Chroma Key is Killing Me.....

[r]Evolution wrote on 2/27/2004, 7:15 PM
(sing the Subject line of this over & over to feel the frustration I'm feeling.)

I'm trying to get a decent Chroma Key for a talking head piece. Our background is lit evenly with Kino Flo's & our talent is pretty well lit also. So far I've got her looking pretty good but her edges are still 'Jagged' and sometimes 'Fuzzy' when I try to Blur them to blend. I've noticed that the Sony Chroma Key does not have a 'Choker'. What would be my other options for getting a good key provided I have good source?

At first I just had the ChromaKey on the video and adjusted then tried the Secondary Color Corrector after that. Results were not a 10. (My boss says it's an 8.) After watching some of Spot's video I moved the SecondaryColorCorrector before the Keyer. I notice that this changes the Hue of the GreenScreen/Background in some places but not evenly. Is this my goal with the SecondaryColorCorrector before the ChromaKeyer? Am I trying to make the Green 'Pop' more and be even? Then after I do that I select the 'Pop' Green color and key.

I've seen some of you guys work and your ChromaKeys come out pretty good. Spot's was excellent in the DVD even with substandard lighting. Am I at least heading in the right direction? Please let me know what the typical chain of ChromaKeying would be.

Thanks in advance!

Comments

SonyEPM wrote on 2/27/2004, 8:36 PM
Make sure your subject isn't wearing anything close to the key color.

Light the backgound as evenly as you can.

Keep the subject as far off the background as you can to avoid green/blue (key color) spill. If there's light falloff, shadows or whatever outside the critical keying area, crop that out.

Prior to the chromakey filter, I use a light gaussian blur for the ckey color only (like, green only, .002-.004). This really helps smooth out the DV jags.

Apply filters at the event level as opposed to track level. Event-level filters can be applid pre- or post- pan/crop. You might not need this, but at least know its there.

Lastly, not every background is going to work with every fg, doesn't matter if you're George Lucas with the best of gear, 2 thousand lights and 50 grips. Be willing to modify the background to suit the foreground image.

When in doubt, blur.
Spot|DSE wrote on 2/27/2004, 9:18 PM
1. Secondary C/C before the key. Use High/low settings on luminance and saturation to make this work. Also, shift the green a little more than you think you might want to.
2. Blur before the key. You can also add about .002/005 of blur on the key dialog itself. I also now have a secret weapon that makes this unnecessary that I hope you'll all see soon. (no, it's not from Sony)
3. I usually render a garbage matte if there is even a HINT of trouble coming.
My rule of thumb on background to subject is that at least the height of the subject should be the distance between back and subject. 6 foot tall guy means 6 feet of distance, period.
Flag the lights hitting the subject so they don't hit the background. Background doesn't have to be as even as you keep hearing/seeing. Those that attended the PPT VASST tour can attest to this. I regularly use wrinkley fabric. Not a good PRACTICE, but point is, I can.
There is a really good article on a homemade chromakey here:
http://www.espvideographics.com/dtr/garage.html
[r]Evolution wrote on 3/2/2004, 8:30 AM
So you guys use the Sony Chroma Key w/2ndary CC & a bit of Blur and get optimal results, right? I noticed in your DVD Spot that you really hoooked it up with less than desirable lighting, so I'm definitely gonna be swapping up my chain to match what you've suggested. I'll post again within a few days to let you guys know how it all went.

Thanks Very Much! Hopefully now people won't be able to tell my GreenScreening from my actual set shots.
Cheno wrote on 3/2/2004, 9:29 AM
All of the above and make sure you have a nice rim light for talent / background separation. This has saved my bacon many times and has prevented jaggies for me.

Mike